Resonant wave guide switching



w. F. KANNENBERG 2,466,439 l April 5, 1949.

I RES'ONANT WAVE GUIDE SWITCHING 2 Sheets-Sheet l Filed April 27, 1944 W KNA/ENBERG BV I I AHORA/Er April 5, 1949 v w. F. KANENBERG 2,466,439

RESONANT WAVE GUIDE SWITCHING Filed April 27, 1944 2 Sheets-Sheet 2 /A/l/ENTOR W. F KANNENBEG A TTOfQ/VE V Patented Apr. 5, 1949 UNITED STATES AT T OFFICE RESONANT WAVE GUIDE SWITCHING Application April 27, 1944, Serial No. 532,979

1 Claim.

This invention relates to coupling devices and more particularly to retractile coupling devices for electrical resonance chambers.

An object of the invention is to provide a coupling device which may enable variation of the coupling of an external circuit to be made to the electromagnetic eld within an electrical resonancechamber.

, Another object of the invention is to permit variation of the tuning of an electrical resonance chamber without affecting the coupling to an external circuit.

An additional object of the invention is to permit the coupling to an electrical resonance chamber to be made ineffective at will.

A still further object of the invention is to insure that a coupling device associated with the electromagnetic lield of an electrical resonance chamber may be maintained in a definite positional relationship with respect to the lield.

Electrical resonance chambers are capable of wide application in the microwave eld. They are only useful when capable of being coupled to an external eld or circuit. In some cases it is important that the coupling employed be of such type as not reduce seriously the selectivity or effectiveness of the resonance chamber. At times it may also be desirable to vary the coupling or to render it wholly ineffective. It is frequently important that during such operations the relative position of the coupling device shall remain such that upon readjustment toy its original position it shall sustain the same relation that it originally had with reference to the internal electromagnetic lield of the resonance chamber.

In accordance with the invention, the coupling is attained by a small energy pick-up capable of effective energy transduction between the internal electromagnetic eld and an external electrical circuit or system to which the pick-up is connected. The pick-up is small enough to be projectable through avery restricted aperture in a wall of the resonance chamber. In a simple embodiment the pick-up device may be slidably mounted to project through the aperture into the interior iield or be withdrawn therefrom at will. Movement of the pick-up device may be effected by a remotely controlled device.

In the drawing, Fig. 1 illustrates a variable frequency electrical resonance chamber coupled to external input and outputcircuits by manually controlled retractile loops;

Fig. 2 illustrates a detail .of the coupler of Fig-1; Y

Fig. 3 is a modification of the coupling structure of the disclosure of Fig. 1 in which the in-v put circuit energy pick-up device is operated by a remotely controlled solenoid;

, Fig. 4 is a section of the resonance chamber in the plane 4-4 of Fig. 1 viewed in the direction of the arrows;

Fig. 5 is a modilication of the coupling structure of Fig. 3, in which the magnetic loop is provided with a parallel spring support to insure' maintenance of correct position of the loop;

` Fig. 6 is a bottom plan view of the apparatus y of Fig. 5 viewed from the horizontal plane 6--6 l tion of the coupler of Fig. 5, in which for oscilla-` fsa tions of a diiierent mode a half dipole replaces the magnetic loop as an energy transfer device. I Referring to Fig. 1, there is shown an energy transducing antenna with a coaxial connecting circuit leading to a hollow resonance chamber with the output circuit of which is associated a rectifying detector and meter. The hollow resonance chamber l comprises a cylindrical member 2 of conducting material having one end closed as at 3 and the other end provided with a liangell to which the cover plate 5 may be tightly clamped by bolts or screws 6. member 2 and the cover 5 may consist of brass,

. copper, spun aluminum or other metallic material having good electrically conducting proper V ties.

trical resonance chamber, as is well known, has a plurality of natural resonance frequencies depending upon its conformation and tuning.

Among the modes of oscillation of resonance' chambers are two general types known respec-v tively as transverse electric, TE and transverse magnetic, TM. For the case of cylindrical resonators the direction of wave propagation is deemed to be along the longitudinal axis of the cylinder.. Transverse electric oscillations for such a resona-Y tor are those in which the electric vector lies wholly in the plane transverse, that is, perpendicular to the longitudinal axis. Transverse magnetic oscillations are those in which the magnetic vector lies wholly in a plane transverse to the longitudinal axis.

netic oscillations, three subscripts Will'be used. The rst is a function of angular displacement in the plane `transverse to the longitudinal axis I The cylindrical The interior surface of the member 2 is as' smooth as possible and for the purpose of in-j creasing its electrical conductivity is preferablyl coated or plated with silver. Such a` closed elec- I In designating particular modes of transverse electricor transverse magnated as TEM or TEnz, respectively, if, in travelingradially from the center to the outer perimeter of the transverse section the electricforce undergoes one or two half cyclesof variation. Likewise, a transverse electricA wave TEM will be. designated as TEon or TEmz, if, .inpassing from,

the central point at one end of the longitudinal axis to the central point at the opposite end of the longitudinal axis the electric intensity undergoes one half cycle or two half cycles variation. When, therefore, reference is made to oscillations ofTEmn mode oscillation, it will be understood that the electric vectors lie wholly in transverse planes; that there is.no change of phase of the electric force in an angular direction about `one of.' the ytransverse planes but'there is a half cycle phase variation in passing 'from the center tothe circular boundary of the transverse section and there are n onehalf cyclesvariation of electric intensity in passing along the longitudinalaxis from one end"ofthe:resonator to the other.

In order to. vary the natural frequency of a desired; mode of oscillation there may be provided a movable circular piston 1 positioned to fltI loosely within the" cylindrical member 2 and, like member t 2, consisting. of electrically conducting materialwith' a platingof silver'on its interior surface. The piston is maintained in position Ibyja pistonV rod 8' of tubular form welded orV soldered to theupper surface of the piston 1 and fitting closelywithin thetubular guide 9 which:

isrigidly connected,'as by screw'threading its end portion, to the cover plate 5. Projecting upwardly from the cover plate 5 is a vertical supporting columnA lattached to the'cover plate in any desiredrnanner and provided'with` a pivot I I which serves as a supporting fulcrum for a` rhomboidal mounting frame l2; At theother end of theframe I2'is a slot |'3v positioned astride of a pin I4 carried by the internally threaded adjustin'g nut I5'with the threaded portion of which a manuallyoperated'screw I6 engages to move the nut upwardlyor downwardly along the conning guide member I1. The screw I6 rests-at its lower endV on a bearing' plate I8 on the upper surface ofj'co've'r 5. At itsupper endscrew I6 is provided with a .calibrated adjusting head I9 adjacent the supporting frame 2Il which extends laterally from the upper end of guide I1'. The screw passes through an aperture in the arm 2I)I and is held in position with respect to the arm by means of the head' I9 and a collar 2| beneathV the arm.

Mounted on the back of the frame I2 is an electric motor 22 `having a horizontal shaft' extending through the frame and carryinga crank;

v 33 of dielectric material. 10`

vided a dipole antenna or energy pick-up 21 associated with a parabolic reflector 28 in, wellknown manner. Connected to the dipole 21 is a coaxial conductor 29, the inner end of which is provided with a brass terminal block 30 of the type shown in section in Fig. 2. The coaxial conductor, 29 comprises an inner conductor 3l, an outer conductor 32 and a surrounding covering The terminal block 30 is -hollow to provide a chamber within which the conductors 32 and 3l' may be connected to the terminals of a long thin -coupling loop 34 projectingupwardly through an orifice 35 in the upper Surface of ,theblock 30. Block 30 is mounted to slide in a vertical direction within the rectangular interior guide-way of a hollow support 36 xedly attached to the lower surface 3 of the chamber I. Support 3S is so positioned as to bring the end of the long narrow loop 34 into substantialalignment with an elongated opening 31 in the lower end 'of chamber I. The terminal block 39 is provided at its lower end With a flanged cylindrical extensionV 38 about which is coileda retractile spring 39 fitting between the flange and the end of support 36 in such manner as to drawl block 3B downwardly within the guiding support 36 to maintain the loop 34 withdrawn from the aperture 31. Pressure against the ilanged end of extension 38 may over-come the retractile effect of spring 39 to project the tip of loop 34'- through the opening 31 intoA the resonance chamber. While in this positionthe loop 34 serves effectively to couple the dipole 21'and the circuit of its coaxial conductor 29'withthe, internal field of the vresonance chamber. If'it is desiredto maintainA the coupling for an indefinite period, the terminal block 39 may be locked in its upward position by tightening a wing nutI llto clamp against the exterior of the support' 36. Wing' nut 4I! is positioned on a screwthreaded stub-4I integral with terminal'bloclr 30 and extending outwardly therefrom through a vertical slot-in the side of support 36. If it be desired to uncouple the loop 34 it is merely necessary to loosen the Wingnut 49 whereupon retractile spring 39 serves to withdraw the` couplingloop 34 from the aperture 31.

For coupling the resonance chamber I to a measuringcircuit, there is provided a second supporting member 43 with a loopA coupling devicesimilarin all respects to the coupling device described" in connection with support 3S. This second couplingdevice involves a loop 44 projectable` through an aperture 45 at the oppositeA side of the lower end of chamber I. Coupling loop 44 is connected through a coaxial conductor 43 and a stopping condenser 41 with a crystal rectii'er 48 andshunting milliammeter 49 of a type well known in high frequency measuring technique. It will be apparent, therefore, that therectifier 48- and the meterl 49 may be maintained effectively connected to or disconnected from the'electromagnetic eld Awithin chamber I* irrespective of the connection to that same electromagnetic fieldof the circuit of dipole'E'l.

Apertures 31 and 45 are preferably made suiciently small to preclude substantial transfer ofenergy'therethrough except as the energy mayr be conveyed by the magnetic coupling loop. TheI apertures are, however, made with adequate separation tov prevent excessive' electrostatic coupling between-the loops 34 and 44 in orderto coni-lne transfer of energyto that induced in each loopby the action'of the magnetic held which it intercepts. The elongated apertures through which the loops pass are' positioned at points at which the intensity of the magnetic eld is relatively high. In the case of TEoin type oscillations for which the particular embodiment of the resonance chamber I illustrated in Figs. 1 and 2 was designed the apertures are preferably located at approximately .48 R from the center where R equals the radius of the interior surface of circular bottom plate 3. Moreover, the plane of each loop and, consequently, the longer direction of the aperture through which it passes is tangential to the circular electric vector of the TEon-l mode oscillation, energy of which it is desired to transfer.

In operation the apparatus of Fig. 1 may be used as a phantom target in a test system of an object locator using electromagnetic wave echoes or it may be employed as a wave meter or tuning calibrator. When in use as a phantom target for an object locator, the locking wing nut 50 may be loosened to permit the circuit of meter 49 to be uncoupled. During the test the extension 38 may be pressed upwardly or, if desired, may be locked in position by wing nut 40 to maintain the coupling of loop 34 to the interior electromagnetic field. Under these circumstances, oscillation energy picked up in the form of pulses from the object locator transmitter is transferred through the loop 34 to the interior electromagnetic field which will build up in intensity f to a magnitude determined by the intensity and duration of the object locator pulses and, also, by the degree to which the frequency of the incoming pulse oscillations correspond with a natural resonance frequency of the chamber I. .As-

suming that the motor I3 is not in operation, the response of the resonance chamber I and the peak intensity of the field excited therein by the incoming oscillations will depend upon the position of plunger 1. It is possible by adjustment of the rotating head I9 to move the frame I2 upwardly lor downwardly carrying along with it the piston 1 to a position such that the intensity of the oscillating field .may be increased. Immediately upon cessation of the incoming pulse, the eld which has been built up within the chamber I will serve as a source of outgoing oscillations which will be transmitted from the dipole 21 back to the object locator receiver to simulate a reflected pulse with substantially no time delay. As long as the oscillation within chamber I persists in any substantial magnitude energy will continue to be radiated from the dipole 21. This period of emission from the dipole 21 of energy stored up within the resonance chamber I corresponds to the time of vibration of a bell or a tuning fork and in the parlance of operators of such test apparatus is known as the ringing time of the resonance chamber. At the cathode-ray oscilloscope of the object locator device, the energy received from the chamber I via the dipole 21 provides an indication extending from substantially zero range to a range corresponding to the limit of the ringing time. For example, if the maximum limit of the ringing time discernible above the noise effects be 20 microseconds it will yield a line indication extending out to the point which would be indicated in the case of reflection from an object two miles distant from the object locator.

It may transpire that it is desired to make a test of an object locator while the locator is aloft in an airplane. Under such circumstances any interference with the normal object loca- 6 tion operation of the device must be reduced to a. minimum. Under these circumstances it may become desirable to tune the resonance chamber very rapidly over the range which may be had by oscillation of the piston 1. This may be done in systematic manner by energization of the motor I3 by the operation of a remotely positioned key in circuit with the motor I3 and a suitable source of energizing current. Upon energization of the motor I3, the crank pin 23 is caused td traverse a circular course with consequent reciprocation of the supporting strap 24 and of the piston 1. The upper limiting position of the piston 1 determines the minimum resonance frequency of the chamber, the lower position its maximum resonance frequency. The range between these frequencies may be of the order of.' 10 megacycles and in any event should be adequate to include the transmitter frequency if the resonance chamber was properly tuned to the transmitter while on the ground. It is possible for one skilled in the interpretation of the visual pattern onl the cathode ray oscilloscope to readily determine if the frequency of incoming pulse oscillations is at one extreme of the range of chamber I or the other or at an approximately central point. While this determination is being made and without in any way interfering with it, the operator may manipulate the cap I9 -of the screw I6 to shift the resonance frequency range of resonance chamber I in such direction as to bring either one of the limiting frequencies or its approximately central frequency into substantial agreement with the incoming oscillations. This adjustment would ordinarily be made on the ground where the adjusting cap I9 is readily accessible to an attendant. This device may enable the central frequency of the resonance chamber to be shifted over a range of the order of 100 megacycles.

By coupling both loops 34 and 44 to the interior electromagnetic field of the chamber I, the chamber may be used as a frequency selective device to constitute in conjunction with rectifier 48 and meter 49, a wave meter. For this purpose the adjusting head I9 of the screw I6 and the adjacent frame 20 .may be calibrated in any suitable manner.

In the event that the position of the resonance chamber I is remote from the observer of the object locator test apparatus or the meter 49 it may become desirable to provide a remotely controlled disconnect for enabling the loop 34 to be connected to the eld of the chamber I at will. Such a structure is shown in Fig. 3 in which the terminal block 30 is carried at the upper end of the plunger 52 of a solenoid 53 connected by bolts 54 extending from the shell of the solenoid 53 through slots in the support 55 attached tov the lower end of resonance chamber I. The solenoid plunger 52 is provided at its lower end with a cylindrical retracting head 56 and retractile spring 51 entirely analogous to the corresponding structure of Fig. 1. In series with the winding of solenoid 53 is a circuit 58 including a source 59 of electrical energy and normally open key 60. The frame of the solenoid 53 is adjustable in the direction of the resonance chamber I in order to enable correct normal positioning of the loop 34 with reference to aperture 3'I. This adjustment is effected by loosening the nuts of bolts 54 and operating the knurled head of adjusting screw 6I to bring solenoid 53 to the correct position whereupon the nuts on the vbolts 54 are clamped tightly. At this position the immersion of 3'4in the electric eld should be such as to result in maximum ringing time.

It will be apparent that in the unenergized condition of solenoid 53, loop 34. will be effectively disconnected from the electromagnetic field of chamber l. Upon actuation of the key 68, the solenoid will be energized to project loop 34 through the opening 3]. The coupler 43 may be identical with that of Fig. 1 or, if desired,fit may be provided with an independent remote control device corresponding to the solenoid 53.

Fig. 5 illustrates a modification of `the structure of Fig. 3 in which the terminal block 30 is supported by a pair` of flat inextensible resilient spring members 63, the outer ends of which are clamped in an obvious manner in the frame 64 attached to the lower portion of resonance chamber l. The supporting action of the springs 63 is such that upon movement of the block 30 upwardly to project the loop 34 into the resonance chamber, the parallel positioning of the members 63 holds loop 34 constantly in a vertical position. This is a simple and effective device to prevent angular dislocation of the loop with respect to the aperture. In the case of relatively long spring supports 63, the shift of the position of loop 34 in a radial direction with respect to the mounting center at the frame 84 is insuicient to cause serious disturbance.

In this structure terminal block 30 whichprovides the housing for loop 34 and which is carried by the springs 63 is not attached to the plunger 65 of solenoid 58. The resilience of springs 63 and their initial bias is such as to hold the terminal block 39 with its coupling loop 34 away from the aperture 3T and in contact with the end of the plunger 85. This structure has the highly advantageous feature that commercial solenoids may be employed with mountings which do not permit precise alignments since the only function of the solenoid plunger in the structure of Fig. 5 is to exert an upward thrust against connector block 38 and the point of application of that thrust is in no way critical. As in the case of Fig. 3, upon closure of the key 68, solenoid 66 is energized to attract plunger 65 upwardly against retractile action of spring 61 thus moving the terminal block 30 upwardly to carry the loop 34 through the aperture 31 into effective magnetic coupling position with the interior Velectromagnetic field of resonator l.

As indicated in Fig. 6 which shows a plan view of the structure of Fig. 5 looking upwardly from beneath the structure, the solenoid 66 and the coupler 43 are arranged not at diametrically opposed positions as in Figs. 3 and 4 but at radial positions separated by 90 degrees.

Fig. 7 illustrates a modification of the structure of Fig. 5 in which, in lieu of the loop coupler 34,

there is employed a device of the half dipole or` probe type` for couplinglwith the electric flel'dinthe manner of an ordinary dipole antenna. As illustrated in Fig. '7, the coupling element comprises a very small rod 88 of` conducting material electrically connected to the central conductor of the coaxial conductor 29. The springs B3 serve to maintain the proper positioning of terminal block 39 and of the small coupling antenna 68 with reference to the electric field within the cham ber I. Since the half dipole 68 is only efective for modes of oscillation in which there is an electric vector paralleltothe half dipole, this device would not be used for TEo1 modes of oscillation but could be employed for certainnther modes such as the TM modes.

What is claimed is:

In combination, an electrical resonator comprising a hollow substantially closed cylindrical chamber 'ofhigh Q adapted tosustain within its interior space electromagnetic oscillations of a natural resonance frequency and the TEom mode, said chamber havingplane circular end walls of radius R and having its interior space between said end walls substantially free of energy absorbing material, one of said end walls having an elongated aperture located at approximately .48B from the center of the end plate and disposed with its longer dimension perpendicular to the radius, an external circuit, and a retractable switch for coupling and uncoupling said circuit to the TEnin mode through said aperture, said switch comprising a loop, whose plane is tangential to the iield pattern of the TEmn mode, the dimensions of said aperture being sufficiently small to preclude substantial transfer of energy therethrough except as may be conveyed by said loop.

WALTER F. KANNENBERG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,437,724 Creveling Dec. 5, 1922 2,016,604 Karnell Oct. 8, 1935 2,311,520 Clifford Feb. 16, 1943 2,342,896 Salzberg Feb. 29, 1944 '2,378,944 Ohl June 26, 1945 2,417,542 Carter Mar. 18, 1947 2,418,839 Julian Apr. l5, 1947 2,427,107 Landon Sept. 9, 1947 2,431,941 Kihn Dec. 2, 1947 2,439,388 Hansen Apr. 13, 1948 FOREIGN PATENTS Number Country Date 116,110 Australia Nov. 4, 1942 

